Non-redox Oxy-Insertion via Organometallic Baeyer–Villiger Transformations: A Computational Hammett Study of Platinum(II) Complexes

Abstract

A Hammett analysis of platinum-mediated oxy-insertion into Pt–aryl bonds is performed using DFT calculations. Modeled transformations involve the conversion of cationic PtII-aryl complexes [(Xbpy)Pt(R)(OY)]+ (R = p-X-C6H4; Y = 4-X-pyridine; Xbpy = 4,4′-X-bpy; X = NO2, H, NMe2) to the corresponding [(Xbpy)Pt(OR)]+ complexes via an organometallic Baeyer–Villiger (BV) pathway. Computational modeling predicts that incorporation of an electron-deficient NO2 group at the 4-position of pyridine-N-oxide lowers the activation barrier to the organometallic BV transformation. In contrast, computational studies reveal that increasing the donor ability of the migrating aryl group, by placement of NMe2 at the para position, lowers the activation barrier to the oxy-insertion step. The impact on the calculated activation barrier is greater for variation of the R group than for modification of Y of the oxygen delivery reagent. For the p-NO2/p-NMe2-substituted aryl migrating groups (R), the ΔΔG‡ for X = NMe2 versus X = NO2...